1. Field of the Invention
The present invention relates to a method and an apparatus for charging a high-viscous material, namely, putty into a service tank, or a putty tank. The putty is used as a material for correcting the dynamic unbalance of a rotary body. The putty is supplied from the putty tank to a rotary body little by little.
2. Description of the Related Art
The putty is attached to a necessary portion of a rotary body so as to use it as a weight for correcting the dynamic unbalance of the rotary body. The viscosity of the putty is as high as more than 4000 poise (at 30.degree. C.) and has thixotropy so that it is not deformed or scattered even though the rotary body rotates. Thixotropy is that viscosity becomes low when the putty is moved by external force and becomes high when it is left to stand. The putty is used in an amount as small as several milligrams to several grams per rotary body. Therefore, the putty is supplied little by little from the putty tank to the rotary body through a nozzle by a microgear pump.
The amount of the putty to the putty tank is limited because it has thixotropy and is supplied therefrom to the rotary body by the microgear pump. Therefore, when the amount thereof becomes small, the putty tank is required to be replenished. However, the replenishment of the putty into the tank is accompanied by difficulty due to the high viscosity of the putty.
In order to overcome this problem, the putty is put into the putty tank with a tool such as a spoon or a spatula or the putty is squeezed out of a vinyl bag into the putty tank after it is put into the vinyl bag. Otherwise, the putty is fed into the tank by a high compression pump.
However, according to the above conventional method for charging the putty into the tank, plenty of air is taken into the tank with the charge or feeding of the putty into the tank. Therefore, the following phenomena occur when a high-viscous material such as the putty is discharged from the tank by a microgear pump and the like.
1. Only air is discharged from the tank while the putty is not discharged therefrom.
2. The amount of the putty discharged from the tank is not uniform before and after the putty is not discharged from the tank due to the existence of air which is taken into the tank in putty charging operation as well as air which is in the tank prior to the charge of the putty into the tank.
3. In discharging the putty from the charging tank, compressed air in the putty forces the putty to extrude from the nozzle even though the discharge pressure is set to zero.
4. The amount of the putty discharged from the tank becomes nonuniform according to the fluctuation of air which has permeated into the putty.
As described above, due to air which has permeated into the tank, the discharge amount of the putty does not accord with a predetermined amount, the discharge of the putty from the tank is interrupted, or the putty is discharged undesirably. As a result, an operation for correcting the dynamic unbalance of the rotary body cannot be appropriately accomplished.
In order to solve this problem, Japanese Patent Laid-Open Publications No. 58-183402 and 63-33202 disclose methods for sucking a high-viscous material, or putty into the tank by generating a negative pressure in the tank.
However, the above methods have the following problems:
1. It is impossible to remove air which has permeated into the high-viscous material being prepared.
2. When a negative pressure is generated in the tank to suck the putty into the tank, the maximum gauge pressure is minus one atmosphere, so that this method cannot be carried out for the high-viscous material of more than 4000 poise.